Template:Chapters 8.16
8.16 - Pressure cooker to reduce cooking fuel
Gryphon Theriault-Loubier, University of Guelph, Canada
Source:https://en.wikipedia.org/wiki/File:Pressure_cooker.jpg
Suggested citation for this chapter.
Theriault-Loubier,G (2022) Pressure cooker to reduce cooking fuel. In Farmpedia, The Encyclopedia for Small Scale Farmers. Editor, M.N. Raizada, University of Guelph, Canada. http://www.farmpedia.org
Introduction
Pressure cookers are well known to many as a stove-top implement which decreases cooking time. They are essentially a sealed cooking pot that maintains a pressure of about 15 pounds per square inch (psi) internally. This pressure increases the boiling point of water, which increases the internal temperature of the pot. There is a pressure release valve to ensure safety. Pressure cookers require approximately 50% of the energy necessary to cook rice as compared to conventional stove-top cooking (Das, 2006). They also save approximately 50% in cooking time (Das, 2006; Sinha, 1991). In India, van Elsland (2011) found that owning a pressure cooker benefitted the most food-insecure families the greatest, as there tends to be a correlation between fuel availability, either for purchase or harvest, and food insecurity. It was also found that in the context of this study, 35% of families had to skip a meal due to fuel shortages.
Practicality and Food Safety
Globally, hundreds of millions of poor people live in high altitudes including in Central America, East Africa and South Asia. The USDA (2011) notes that at altitudes above 2,500 feet (762 meters) the atmosphere becomes much drier on average, such that uncovered food will evaporate water quickly and dry the meal out. Pressure cookers are excellent at retaining moisture in foods so long as the heat is reduced once pressure is reached (Pokharel, 2004). In terms of food safety, higher altitudes limit the ability of heated water in destroying pathogens (USDA, 2011). While water boils at around 100°C (212°F) at sea level, with every 500ft (152 meters) increase in elevation, water boils at approximately 1°F lower. At 5000ft (1524 meters), food will require approximately 25% more cooking time than sea level to compensate; a food thermometer is recommended by the USDA as the only reliable way to determine if food has reached a safe internal temperature (160°F or 71°C). Hence, increasing the ambient pressure of food through the use of a pressure cooker will have significant benefits at high altitudes.High Altitude Benefits
Pokharel (2004) conducted research on a variety of cooking methods in the Banepa and Dhulikhel municipalities of Nepal. These municipalities are approximately 5,000 feet (1524 meters) above sea level and have an average household family size of 6.2, making them a good case study for the efficiency of pressure cookers at high altitude. At this altitude, a pressure cooker on a liquid propane stove was able to cook rice in 9.7 minutes, compared to 27.7 minutes using a Karahi (open top pan with curved sides) and traditional fuel wood stove. In a system efficiency test, pressure cookers were found to be more efficient than all other implements on every stove-type at this altitude (Pokharel, 2004). While no data could be found, it would be of great interest to determine the combined effectiveness of a high-efficiency stove with a pressure cooker particularly in a high-altitude environment.
Hence, in places where high altitude communities exist such as Ethiopia, Nepal and Bolivia, a pressure cooker can be considered an essential tool which will save time, fuel and labour while reducing deforestation. In Nepal, a savings of over 55% in energy required to cook food was found, most likely due to its high altitude in cooking (Shaligram, 2002).A possible benefit of using a pressure cooker is the resulting acceptability of some foods that are nutritious and/or suitable for production, consumption and profitability, but which struggle due to cooking constraints. One example of this is bambara groundnut, an indigenous legume in Sub-Saharan Africa which has an exceptional nutritional profile while being drought tolerant. Prior to African colonization, bambara may have been as important to Africa as a protein source as soybeans are to China, and could once again become a mainstay of local diets; however one of the primary constraints is the size of the bean, which is quite large. Hence, bambara requires substantial cooking time, and would require substantially more cooking time at high altitudes.
Where to purchase
While models developed in the past were sometimes dangerous, advancements in technology have reduced risk considerably. A modern pressure cooker will be constructed of stainless steel (18/10 grade) and will have a robust safety valve, as well as secondary fail-safe mechanisms such as a latch to hold the lid in case of valve failure. Some pressure cookers currently on the market are made of aluminum; while these devices are substantially lighter and possibly more affordable, extra care should be taken to determine that these devices are safe since aluminum is fairly soft metal and could fail if not of a high quality construction.In Africa, a household pressure cooker can be purchased for approximately $7-10 USD. A link is provided, but may be out of date by publication. Pokharel (2004) priced rice cookers in the Banepa region of Nepal at 300 rupees, which is approximately $3.50 USD.
Constraints to Development
Pressure cookers require more initial investment than a typical pan of similar size. The gasket or sealing ring on the lid requires special care, including cleaning and occasional lubrication, and will require replacement if visible wear or warping occurs. Some models do not require a gasket or sealing ring. Pokharel (2004) estimated the average life-time of a pressure cooker to be 5 years, with a 50 rupee maintenance cost over the course of the product life-cycle.
Pressure cookers accomplish much the same task as boiling, therefore foods that are meant to be baked or fried will be unsuitable. Certain foods are not well suited to pressure cooking. Typically these foods froth in excess and block the steam vent. Oatmeal is an example of a food that has this trait. To compensate for this, many cookers suggest filling the pot only 1/3 full when using foods that tend to froth. For other foods, a pressure cooker should not be filled beyond 50% capacity to allow for adequate room for food expansion and pressure buildup. Some manufacturers suggest using a teaspoon of oil in the cooking water to keep the frothing down, however users are encouraged to follow manufacturer directions.
Cooking with a pressure cooker may require overcoming fear concerning perceived hazards. It may also require some learning, especially at the beginning, as many foods will become overcooked quickly. Once started, there is no way to check the consistency of food once cooking has begun without first allowing pressure to escape, which essentially stops the cooking process. Usually a model will include instructions, but the foods listed might not be local foods or may not be in the local language, so instructional use may be needed.
Picture Based Lesson to Train Farmers
For the South Asian version (pictures only, text for you to insert), click this link for lesson 9.16:http://www.sakbooks.com/uploads/8/1/5/7/81574912/9.16_south_asian.pdf
For the East/South Asian version (pictures only, text for you to insert), click this link for lesson 9.16:http://www.sakbooks.com/uploads/8/1/5/7/81574912/9.16e.s.a.pdf
For the Sub-Saharan Africa/Caribbean version (pictures only, text for you to insert), click this link for lesson 9.16:http://www.sakbooks.com/uploads/8/1/5/7/81574912/9.16subsaharan_africa_carribean.pdf
For the Latin-America version (pictures only, text for you to insert), click this link for lesson 9.16:http://www.sakbooks.com/uploads/8/1/5/7/81574912/9.16latin_america.pdf
For North Africa And Middle East version (pictures only, text for you to insert), click this link for lesson Chapter 5. 8.11:http://www.sakbooks.com/uploads/8/1/5/7/81574912/8.11n._africa_middleeast.pdf
Source: MN Raizada and L Smith (2016) A Picture Book of Best Practices for Subsistence Farmers. eBook, University of Guelph Sustainable Agriculture Kit (SAK) Project, June 2016, Guelph, Canada.
References
1. Das, T., Subramanian, R., Chakkaravarthi, A., Singh, V., Ali, S. Z., & Bordoloi, P. K. (2006). Energy conservation in domestic rice cooking. Journal of Food Engineering, 75(2), 156-166.
2. Pokharel, S. (2004). Energy economics of cooking in households in nepal. Energy (Oxford), 29(4), 547-559.
3. Sinha, C. S., & Kandpal, T. C. (1991). Optimal mix of technologies in rural india: The cooking sector. International Journal of Energy Research, 15(2), 85-85
4. van Elsland, S.,L., van, d. H., Joshi, S., Doak, C. M., & Ponce, M. C. (2012). Pressure cooker ownership and food security in aurangabad, india. Public Health Nutrition, 15(5), 818-26.